Chiron Ends Herpes Vaccine Tests

Emeryville-based Chiron Corp. has ended tests on a vaccine to prevent genital herpes transmission that was to be one of its flagship new products. The news that development work will end because the drug does not work sent the company’s shares down $3.75, or 17%, to $18.125 on Nasdaq. Until it analyzes test results of the failed vaccine, the company said, it won’t start final clinical trials of a vaccine for another herpes virus, cytomegalovirus retinitis, that can cause blindness in people with depressed immune systems. The company said its method of developing genetically engineered vaccines for the herpes viruses may not be effective.